<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<select name="" id="s1">
    <option value="">北京</option>
    <option value="">天津</option>
</select>
<button onclick="add()">添加</button>

<script>
    function add() {
        window.open('/p2/',"dsdsd","status=1,height:500,width:600,toolbar=0,resizeable=0")
    }

    function xxxxxxxx(name) {
        var option = document.createElement("option")
        option.innerHTML=name
        option.setAttribute("selected",true)
        document.getElementById("s1").appendChild(option)
    }
</script>
</body>
</html>